I would like to backup using Windows Imaging to some kind of NAS appliance. I believe this will require the NAS to support iSCSI. I would then like the appliance to support the replication of the iSCSI LUN to an external eSATA or USB disk connected directly to the appliance.

I've found plenty of NAS appliances that can do iSCSI and replicate to an external drive, but none that I've found thus far can do both at once. That is, the devices can do iSCSI, but then the replication feature doesn't work.

The idea here is to backup to an appliance located in a secure office far away from the server room. Offsite backups to external hard drive could be managed from the appliance. The benefits of such a setup would be: 1) very unlikely that fire or random theft would affect both server-room backup and "remote" backup appliance 2) offsite backups could be managed by multiple trusted people without granting access to server room 3) Windows imaging provides poor man's deduplication, so each backup volume can contain a decent backup history.

I understand why this would be a non-trivial thing to implement, but I'm wondering if such a thing exists? Preferably a tabletop, low to medium cost device.

Alternative solutions welcome. NOTE: I'm backing up very few but very large files, so file replication is not a good option.